Phosphor and fluorescent lamp using the same

ABSTRACT

According to the present invention, there is provided a phosphor represented by a general formula (Ba w  Ca x  Mg y  Eu z )O.aAl 2  O 3 . bSiO 2  where 0.1≦w≦0.5, 0.0004≦x≦0.0020, 0.1≦y≦0.8, 0.03≦z≦0.10, w+x+y+z=1, 1.5≦a≦4.5, and 0.0005≦b≦0.0030. The present invention provides a blue-color light-emitting aluminate phosphor which has a high emission output and a low decrease in its emission intensity during use, and a fluorescent lamp using the same.

BACKGROUND OF THE INVENTION

The present invention relates to a blue-color light-emitting aluminatephosphor and a fluorescent lamp using the same.

Recently, demand has arisen for general illumination fluorescent lampshaving high output and high color-rendering properties. This demand ismet by three-band type fluorescent lamps wherein blue, green, and redphosphors, having emission spectrum distributions of relatively narrowwavelength ranges, are mixed in an appropriate mixing ratio.

A recent three-band type fluorescent lamp uses an aluminate phosphor asa blue-color light-emitting component. However, a europium-activatedaluminate phosphor [(Ba,Eu)Mg₂ Al₁₆ O₂₇ ] (Japanese Patent Publication(Kokoku) No. 52-22836) as a known blue phosphor is not satisfactory,since its emission intensity descreases during use. Othereuropium-activated aluminate phosphors [(Ba,Eu)O.eAl₂ O₃.fy₂ O₃ ](Japanese Patent Disclosure (Kokai) No. 60-139784) and [Ba_(1-g-h)Sr_(g) Mg_(i).Al_(j) O_(1+i+j/2) :Eu_(h) ²⁺ ] (Japanese PatentDisclosure (Kokai) No. 56-86982) are also not satisfactory since theiremission intensities are low and decrease during use.

The emission colors of the respective phosphors of these types offluorescent lamp differ greatly. When the emission outputs (emissioninensities) of the respective phosphors decrease while the lamp is inuse, color deviation occurs, degrading the color rendering properties.

Japanese Patent Disclosure (Kokai) No. 57-207678 discloses a fluorescentlamp having a combination of 3(M,Eu)₃ (PO₄)₂.m'Cl₂ or k(M_(1-o) Eu_(o)O).lP₂ O₅ mM'X₂.nB₂ O₈ as a blue phosphor, (Re_(1-p-q-r) Tb_(p) Ce_(q)As_(r))₂ O₃ μSiO₂.νP₂ O₅ as a green phosphor, and (Y,Eu)₂ O₃ as a redphosphor. With this lamp, however, color deviation occurs during use,due to a difference in the degradation rates of the respectivephosphors, thus a decrease in the total luminous flux intensity of thelamp is large.

SUMMARY OF THE INVENTION

The present invention has been developed to solve the above problems,and has as its object to provide a blue-color light-emitting aluminatephosphor which has a high emission output and a low decrease in itsemission intensity during use, and a fluorescent lamp using the same.

The phosphor of the present invention is a blue-color light-emittingaluminate phosphor represented by a general formula (Ba_(w) Ca_(x)Mg_(y) Eu_(z))O.al₂ O₃.bSiO₂ where 0.1≦w≦0.5, 0.0004≦x≦0.0020,0.1≦y≦0.8, 0.03≦z≦0.10, w+x+y+z+1, 1.5≦a≦4.5, and 0.0005<b≦0.0030.

It is preferable that a satisfies 2.0≦a≦3.0 and that x satisfies0.0006≦x≦0.0015.

Eu can be partially substituted by Mn. The substitution ratio of Mn istwice or less than Eu in molar ratio. In this case, coefficient zdepends on the total amount of Eu and Mn.

The phosphor (Ba_(w) Ca_(x) Mg_(y) Eu_(z))O.aAl₂ O₃.bSiO₂ of the presentinvention can be synthesized as follows:

In selecting phosphor materials, at least one member selected from thebarium compound group consisting of barium oxide, barium hydroxide,barium carbonate, and so on can be used as a barium source; at least onemember selected from the calcium compound group consisting of calciumoxide, calcium hydroxide, calcium carbonate and so on can be used as acalcium source; at least one member selected from the magnesium compoundgroup consisting of magnesium oxide, magnesium hydroxide, magnesiumcarbonate, and so on can be used as a magnesium source; at least onemember selected from the europium compound group consisting of europiumoxide, europium fluoride, and so on can be used as a europium source; atleast one member selected from an aluminum compound group consisting ofaluminum oxide, aluminum hydroxide, and so on can be used as an aluminumsource; and at least one member selected from the silicon compound groupconsisting of silicon dioxide and so on can be used as a silicon source.

Predetermined amounts of the above materials are weighed and mixedthoroughly. The mixture is put in a refractory container and sintered inair at 1,200° to 1,600° C. for 3 to 4 hours. The obtained sinteredproduct is pulverized and treated by washing with water and so on.

The powder obtained by pulverization is dried and put in the refractorycontainer once again, and sintered in a reducing atmosphere at 1,400° to1,600° C. for 3 to 4 hours. When the sintered product is pulverized andtreated by washing with water and so on, a blue-color light-emittingaluminate phosphor of the present invention can be obtained.

FIG. 1 shows a spectrum distribution of the blue-color light-emittingaluminate phosphor of the present invention. It can be seen from FIG. 1that the phosphor of the present invention has an emission spectrum of anarrow wavelength range in the vicinity of 450 nm.

The fluorescent lamp according to the present invention is obtained bycoating, on the inner surface of a glass bulb, a mixture of the bluephosphor (first phosphor); a second phosphor having an emission spectrumin a visible green color range and represented by a general formula Ln₂O₃.c(Mg_(1-u) Ca_(u))O.d[(Al₂ O₃)_(1-v).(SiO₂)_(v) ] (where Ln is atleast one element selected from the group consisting of lanthanum,gadolinium, yttrium, cerium, and terbium, and 1.5≦c≦5.0, 2.5≦d≦14.0,0.001≦u≦0.005, and 0.0002≦v≦0.0010); and a third phosphor having anemission spectrum in a visible red color range and represented by ageneral formula (Y_(1-t) Eu_(t))₂ O₃ (where 0.020≦t≦0.065). The first,second, and third phosphors are contained at ratios of 0.2 to 35% byweight, 35 to 60% by weight, and 30 to 60% by weight, respectively, withrespect to 100% by weight of the mixture.

If the mixing ratios of the first, second, and third phosphors of thepresent invention fall outside the above ranges, the color renderingproperties are decreased.

The second phosphor is disclosed in Japanese Patent Application No.61-120208 by the present inventors.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows the emission spectrum of the blue-color phosphor accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1

    ______________________________________                                        Barium oxide      BaO      68.85 g                                            Calcium hydroxide Ca(OH).sub.2                                                                           0.07                                               Magnesium hydroxide                                                                             Mg(OH).sub.2                                                                           29.17                                              Europium oxide    Eu.sub.2 O.sub.3                                                                       8.80                                               Aluminum oxide    Al.sub.2 O.sub.3                                                                       254.90                                             Silicon dioxide   SiO.sub.2                                                                              0.06                                               ______________________________________                                    

The above materials were mixed thoroughly. The obtained mixture wassintered in air at 1.350° C. for 4 hours. The sintered product waspulverized and washed with water. The powder obtained by pulverizationwas dried and sintered in a reducing atmosphere at 1,400° C. for 4hours. Finally, the sintered powder was pulverized, washed with water,and dried again to obtain a phosphor.

The composition of the obtained phosphor was (Ba₀.449 Ca₀.001 Mg₀.5Eu₀.05)O.2.5Al₂ O₃.0.001SiO₂. The emission intensities of this phosphor,under excitation by the mercury bright line of 254 nm, were 110% and120% those of conventional blue-color light-emitting aluminum phosphors(Ba,Eu)Mg₂ Al₁₆ O₂₇ and (Ba,Eu)O.eAl₂ O₃.fY₂ O₃, respectively. Itsemission intensity after the lamp had been ON for 1,000 hours was 180%that of (Ba,Eu)O.eAl₂ O₃.fY₂ O₃.

EXAMPLE 2

    ______________________________________                                        Barium carbonate  BaCO.sub.3                                                                             39.08 g                                            Calcium oxide     CaO      0.11                                               Magnesium hydroxide                                                                             Mg(OH).sub.2                                                                           40.83                                              Europium oxide    Eu.sub.2 O.sub.3                                                                       17.60                                              Aluminum hydroxide                                                                              Al(OH).sub.3                                                                           546.00                                             Silicon dioxide   SiO.sub.2                                                                              0.12                                               ______________________________________                                    

The above materials were treated following the same procedures as inExample 1. The composition of the obtained phosphor was (Ba₀.198 Ca₀.002Mg₀.7 Eu₀.1)O.3.5Al₂ O₃.0.002SiO₂. The emission intensities of thisphosphor, under excitation by the mercury bright line of 254 nm, was114% that of (Ba,Eu)O.eAl₂ O₃.fY₂ O₃, and was 135% that thereof afterthe lamp had been ON for 1,000 hours.

EXAMPLE 3

    ______________________________________                                        Barium hydroxide  Ba(OH).sub.2                                                                           34.27 g                                            Calcium fluoride  CaF.sub.2                                                                              0.12                                               Magnesium carbonate                                                                             MgCO.sub.3                                                                             62.27                                              Europium fluoride EuF.sub.3                                                                              12.54                                              Aluminum oxide    Al.sub.2 O.sub.3                                                                       203.92                                             Silicon dioxide   SiO.sub.2                                                                              0.18                                               ______________________________________                                    

The above materials were treated following the same procedures as inExample 1. The composition of the obtained phosphor was (Ba₀.2 Ca₀.0015Mg₀.7385 Eu₀.06)O.2.0Al₂ O₃ 0.003SiO₂. The emission intensity of thisphosphor, under excitation by the mercury bright line of 254 nm, was118% that of (Ba,Eu)O.eAl₂ O₃.fY₂ O₃, and was 155% that thereof afterthe lamp had been ON for 1,000 hours.

Table 1 compares the emission intensities of the phosphors (Examples 1to 3, Examples 4 to 16, in accordance with the same manufacturing methodas in Examples 1 to 3) and conventional blue-color light-emittingaluminum phosphors (Controls 1 and 2), and their respectivedegradations. It can be seen from Table 1 that a phosphor of the presentinvention, represented by a general formula (Ba_(w) Ca_(x) Mg_(y)Eu_(z))O.aAl₂ O₃.bSiO₂, has higher emission intensities immediatelyafter excitation and after the lamp has been ON for 1,000 hours. It canalso be seen that these high emission intensities can be obtained when2.0<a-3.0 or 0.0006<x<0.0015.

                                      TABLE 1                                     __________________________________________________________________________                                         Emission Intensi-                                                    Emission Intensi-                                                                      ty After                                 No.  W    X   Y    Z  a b   ty After 0 hrs.                                                                        1,000 hrs.                               __________________________________________________________________________    Example                                                                        1   0.449                                                                              0.0010                                                                            0.50 0.05                                                                             2.5                                                                             0.0010                                                                            120      180                                       2   0.198                                                                              0.0020                                                                            0.70 0.10                                                                             3.5                                                                             0.0020                                                                            114      135                                       3   0.2  0.0015                                                                            0.7385                                                                             0.06                                                                             2.0                                                                             0.0030                                                                            118      155                                       4   0.1496                                                                             0.0004                                                                            0.75 0.10                                                                             1.5                                                                             0.0015                                                                            110      133                                       5   0.3188                                                                             0.0012                                                                            0.60 0.08                                                                             4.5                                                                             0.0022                                                                            117      148                                       6   0.3  0.0017                                                                            0.6283                                                                             0.07                                                                             3.0                                                                             0.0005                                                                            119      175                                       7   0.1492                                                                             0.0008                                                                            0.80 0.05                                                                             1.8                                                                             0.0017                                                                            115      149                                       8   0.2494                                                                             0.0006                                                                            0.65 0.10                                                                             2.3                                                                             0.0025                                                                            121      183                                       9   0.5495                                                                             0.0005                                                                            0.40 0.05                                                                             3.2                                                                             0.0008                                                                            112      135                                      10   0.2  0.0013                                                                            0.7087                                                                             0.09                                                                             2.9                                                                             0.0027                                                                            123      165                                      11   0.5  0.0017                                                                            0.4903                                                                             0.08                                                                             1.6                                                                             0.0016                                                                            110      130                                      12   0.3982                                                                             0.0018                                                                            0.50 0.10                                                                             4.0                                                                             0.0030                                                                            111      132                                      13   0.2585                                                                             0.0015                                                                            0.70 0.04                                                                             3.4                                                                             0.0010                                                                            118      160                                      14   0.1195                                                                             0.0005                                                                            0.80 0.08                                                                             2.8                                                                             0.0009                                                                            120      170                                      15   0.4588                                                                             0.0012                                                                            0.45 0.09                                                                             4.4                                                                             0.0013                                                                            115      150                                      16   0.338                                                                              0.0020                                                                            0.60 0.06                                                                             3.7                                                                             0.0021                                                                            112      141                                      Control                                                                        1   (Ba, Eu)Mg.sub.2 Al.sub.16 O.sub.27                                                                  109      130                                       2   (Ba, Eu)O.eAl.sub.2 O.sub.3.fY.sub.2 O.sub.3                                                         100      100                                      __________________________________________________________________________

EXAMPLE 17

Fifteen percent by weight of (Ba₀.3 Ca₀.002 Mg₀.6 Eu₀.098)O.2.5Al₂O₃.0.0030SiO₂ as a blue phosphor, 50% by weight of (La₀.5 Ce₀.3 Tb₀.2)₂O₃.2.0.(Mg₀.999 Ca₀.001)O.8.0[(Al₂ O₃)₀.9996 (SiO₂)₀.0004 [ as a greenphosphor, and 35% by weight of (Y₀.96 Eu₀.04)₂ O₃ as a red phosphor weremixed together. The mixture was coated on the inner surface of a glassbulb to prepare a fluorescent lamp FL22SS/18 of the present invention.

The color of the light emitted by this fluorescent lamp, after it hadbeen ON for 0 hours (immediately after manufacture) was x=0.340 andY=0.357 on the x, y chromaticity coordinate diagram. After thisfluorescent lamp was ON for 500 hours, the color of its light wasmeasured to be x=0.340 and y=0.359. In contrast to this, the color ofthe light emitted by a lamp according to Control 3 was x=0.340 andy=0.354, after the lamp had been ON for 0 hours, and was x=0.360 andy=0.365, after the lamp had been ON for 500 hours.

The total luminous fluxes (emission outputs) after the lamp had been ONfor 500 hours were 102% and 112% those of Control 3, respectively.

As a result, it is apparent that the lamp of Example 17 has less colordeviation and a smaller decrease in its emission output than the lampaccording to Control 3.

Similar tests were performed by changing the formula and mixing ratio ofthe respective color phosphors (Examples 18 to 31).

Table 2 shows the results in this case. The fluorescent lamps of thepresent invention are superior to that of Control 3, in that their colordeviation and decrease in emission output are less.

    TABLE 2            Total    Emitted Color Emitted Color Total Luminous Blue Phosphor G     reen Phosphor Red Phosphor After 0 hrs. After 500 hrs. Luminous Flux     After   Mixing Ratio  Mixing Ratio  Mixing Ratio (x, y color (x, y color F     lux After 500 hrs. No. Composition (% by weight) Composition (% by     weight) Composition (% by weight) Representation) Representation) 0 hrs.     (%) (%)       Example           17 (Ba.sub.0.3 Ca.sub.0.0020      Mg.sub.0.6 15 (La.sub.0.5 Ce.sub.0.3 Tb.sub.0.2).sub.2 50 (Y.sub.0.960     35 x = 0.338 x = 0.340 102 112  Eu.sub.0.0980)O.2.5Al.sub.2 O.sub.3.     O.sub.3.2.0(Mg.sub.0.999 Ca.sub.0.001)  Eu.sub.0.040).sub.2  y = 0.357 y     = 0.359  0.0030SiO.sub.2  O.8.0[(Al.sub.2 O.sub.3).sub.0.9996  O.sub.3      (SiO.sub.2).sub.0.0004 ]  18 (Ba.sub.0.449 Ca.sub.0.0010 Mg.sub.0.5 10     (La.sub.0.5 Ce.sub.0.3 Tb.sub.0.2).sub.2 60 (Y.sub.0.945 30 x = 0.340 x     = 0.341 101 110  Eu.sub.0.05)O.2.5Al.sub.2      O.sub.3.  O.sub.3.2.5(Mg.sub.0.998 Ca.sub.0.002)  Eu.sub.0.055).sub.2     y = 0.356 y = 0.358  0.0010SiO.sub.2  O.5.0[(Al.sub.2      O.sub.3).sub.0.9998  O.sub.3    (SiO.sub.2).sub.0.0002      ] 19 (Ba.sub.0.198 Ca.sub.0.0020 Mg.sub.0.7 5 (Gd.sub.0.6 Ce.sub.0.3     Tb.sub.0.1).sub.2 55 (Y.sub.0.965 40 x = 0.341 x = 0.343 103 109     Eu.sub.0.10)O.3.5Al.sub.2 O.sub.3.  O.sub.3.3.0(Mg.sub.0.999      Ca.sub.0.001)  Eu.sub.0.035).sub.2  y = 0.353 y =      0.354  0.0020SiO.sub.2  0.10[(Al.sub.2 O.sub.3).sub.0.9990  O.sub.3     (SiO.sub.2).sub.0.0010 ] 20 (Ba.sub.0.2 Ca.sub.0.0015 Mg.sub.0.3385 20     (Y.sub.0.7 Ce.sub.0.15 Tb.sub.0.15).sub.2 35 (Y.sub.0.980 45 x = 0.340 x     = 0.342 100 111  Eu.sub.0.06 )O.2.0AlO.sub.3.  O.sub.3.2.0(Mg.sub.0.995     Ca.sub.0.005)  Eu.sub.0.020).sub.2  y = 0.355 y = 0.356  0.0030SiO.sub.2      O.2.5[(Al.sub.2 O.sub.3).sub.0.9998  O.sub.3    (SiO.sub.2).sub.0.0002     ] 21 (Ba.sub.0.3188 Ca.sub.0.0012 15 (Ce.sub.0.65 Tb.sub.0.35).sub.2     O.sub.3. 40 (Y.sub.0.935 45 x = 0.339 x = 0.340 102 112  Mg.sub.0.60     Eu.sub.0.08)O.  1.5(Mg.sub.0.999 Ca.sub.0.001)O.  Eu.sub.0.065).sub.2  y     = 0.352 y = 0.355  4.5Al.sub.2 O.sub.3.0.0022  4.0[(Al.sub.2      O.sub.3).sub.0.9998  O.sub.3  SiO.sub.2  (SiO.sub.2).sub.0.0002 ] 22     (Ba.sub.0.3 Ca.sub.0.0017 Mg.sub.0.6283 10 (La.sub.0.7 Tb.sub.0.3).sub.2     O.sub.3. 45 (Y.sub.0.975 45 x = 0.342 x =      0.345 101 110  Eu.sub.0.07)O.3.0Al.sub.2 O.sub.3.  5.0(Mg.sub.0.996     Ca.sub.0.004)  Eu.sub.0.025).sub.2  y = 0.350 y = 0.353  0.0005SiO.sub.2      O.8.0[(Al.sub.2 O.sub.3).sub.0.9997  O.sub.3    (SiO.sub.2).sub.0.0003     ] 23 (Ba.sub.0.1492 Ca.sub.0.0008 Mg.sub.0.8 O 10 (Gd.sub.0.8      Tb.sub.0.2).sub.2 60 (Y.sub.0.950 30 x = 0.341 x = 0.344 103 109     Eu.sub.0.05)O.1.8Al.sub.2 O.sub.3.  O.sub.3.3.5(Mg.sub.0.998      Ca.sub.0.002)  Eu.sub.0.050).sub.2  y = 0.358 y =      0.360  0.0017SiO.sub.2  O.12[Al.sub.2 O.sub.3).sub.0.9998  O.sub.3     (SiO.sub.2).sub.0.0002 ] 24 (Ba.sub.0.2494 Ca.sub.0.0006 Mg.sub.0.65 25     (La.sub.0.6 Ce.sub.0.2 Tb.sub.0.2).sub.2 45 (Y.sub.0.970 30 x = 0.340 x     = 0.342 101 111  Eu.sub.0.10)O.2.3Al.sub.2      O.sub.3.  O.sub.3 .4.0(Mg.sub.0.999 Ca.sub.0.001)  Eu.sub.0.030).sub.2     y = 0.354 y = 0.357  0.0025SiO.sub.2  O.11.5 [(Al.sub.2      O.sub.3).sub.0.9993  O.sub.3    (SiO.sub.2).sub.0.0007      ] 25 (Ba.sub.0.5495 Ca.sub.0.0005 Mg.sub.0.40 0.4 (Gd.sub.0.6      Ce.sub.0.3 Tb.sub.0.1).sub.2 39.8 (Y.sub.0.970 59.8 x = 0.483 x = 0.484     109 110  Eu.sub.0.05)O.3.2AlO.sub.3.  O.sub.3 .2.0(Mg.sub.0.995      Ca.sub.0.005)  Eu.sub.0.030).sub.2  y = 0.464 y =      0.467  0.0008SiO.sub.2  O.5.0[(Al.sub.2 O.sub.3).sub.0.9996  O.sub.3     (SiO.sub.2).sub.0.0004 ] 26 (Ba.sub.0.2 Ca.sub.0.0013 0.3 (Y.sub.0.6     Ce.sub.0.3 Tb.sub.0.1).sub.2 O.sub.3. 40.9 (Y.sub.0.975 58.8 x = 0.482 x     = 0.485 110 112  Mg.sub.0.7087 Eu.sub.0.09)O.  1.5(Mg.sub.0.998      Ca.sub.0.002)O.  Eu.sub.0.025).sub.2  y = 0.465 y = 0.468  2.9Al.sub.2     O.sub.3 .0.0027  13[(Al.sub.2 O.sub.3).sub.0.9992  O.sub.3  SiO.sub.2     (SiO.sub.2).sub.0.0008 ] 27 (Ba.sub.0.5 Ca.sub.0.0017 Mg.sub.0.4903 0.2     (Ce.sub.0.75 Tb.sub.0.25).sub.2 O.sub.3. 39.9 (Y.sub.0.980 59.9 x =     0.484 x = 0.487 111 110  Eu.sub.0.08)O.1.6Al.sub.2 O.sub.3.  2.5     Mg.sub.0.996 Ca.sub.0.004)  Eu.sub.0.020).sub.2  y =  0.464 y = 0.466     0.0016SiO.sub.2  O.6.0[(Al.sub.2 O.sub.3).sub.0.9998  O.sub.3     (SiO.sub.2).sub.0.0002 ] 28 (Ba.sub.0.3982 Ca.sub.0.0018 Mg.sub.0.5 O     0.5 (La.sub.0.6 Tb.sub.0.4).sub.2 40.0 (Y.sub.0.950 59.5 x = 0.483 x =     0.484 112 111  Eu.sub.0.10)O.4.0Al.sub.2      O.sub.3.  O.sub.3 .2.0Mg.sub.0.999 Ca.sub.0.001)  Eu.sub.0.050).sub.2     y = 0.463 y = 0.466  0.0030SiO.sub.2  O.2.5[(Al.sub.2      O.sub.3).sub.0.9995  O.sub.3    (SiO.sub.2).sub.0.0005      ] 29 (Ba.sub.0.2585 Ca.sub.0.0015 Mg.sub.0.70 0.3 (Gd.sub.0.7      Tb.sub.0.3).sub.2 41.1 (Y.sub.0.965 58.6 x = 0.483 x = 0.485 110 108     Eu.sub.0.04)O.3.4Al.sub.2 O.sub.3.  O.sub.3.3.0(Mg.sub.0.995      Ca.sub.0.005)  Eu.sub.0.035).sub.2  y = 0.463 y =      0.467  0.0010SiO.sub.2  O.5.5[(Al.sub.2 O.sub.3).sub.0.9996  O.sub.3     (SiO.sub.2).sub.0.0004 ] 30 (Ba.sub.0.1195 Ca.sub.0.0005 Mg.sub.0.80 0.4     (La.sub.0.6 Gd.sub.0.1 Gd.sub.0.2 Tb.sub.0.1).sub.2 40.8 (Y.sub.0.950     58.8 x = 0.482 x = 0.485 109 108  Eu.sub.0.08)O.2.8AlO.sub.3.  O.sub.3     .4.5(Mg.sub.0.997 Ca.sub.0.003)  Eu.sub.0.050).sub.2  y = 0.465 y =     0.469  0.0009SiO.sub.2  O.7.0[(Al.sub.2 O.sub.3).sub.0.9997  O.sub.3     (SiO.sub.2).sub.0.0003 31 (Ba.sub.0.4588 Ca.sub.0.0012 0.3 (La.sub.0.5     Gd.sub.0.1 Ce.sub.0.2 39.9 (Y.sub.0.945 59.8 x = 0.482 x = 0.484 110 110      Mg.sub.0.45 Eu.sub.0.09)O.  Tb.sub.0.2).sub.2 O.sub.3.5.0(Mg.sub.0.999     Eu.sub.0.055).sub.2  y = 0.462 y = 0.465  4.4Al.sub.2 O.sub.3 .0.0013     Ca.sub.0.001)O.14[(Al.sub.2 O.sub.3).sub.0.9991  O.sub.3  SiO.sub.2     (SiO.sub.2).sub.0.0009 ] Control 3 3(Sr.sub.0.98 Eu.sub.0.02 O). 19     (La.sub.0.1 Tb.sub.0.2 Ce.sub.0.697 44 (Y.sub.0.950 37 x = 0.340 x =     0.360 100 100  0.92 P.sub.2 O.sub.5 .0.33  Li.sub.0.003 ).sub.2 O.sub.3.      Eu.sub.0.050).sub.2  y = 0.354 y = 0.365  CaCl.sub.2 .0.08 B.sub.2     O.sub.3  0.9P.sub.2      O.sub.5 .0.2SiO.sub.2  O.sub.3

Table 3 shows the emission outputs (total luminous fluxes) offluorescent lamps, obtained by coating the blue, green, and redphosphors of Example 17 on the inner surfaces of different glass bulbs,immediately after manufacture (after the lamps had been ON for 0 hours)and after the lamps had been ON for 500 hours. The rates of degradationin emission output of the respective phosphors of Example 17 are smallerthan those of the respective phosphors used in the conventionalfluorescent lamp (Control 4), and the rates of degradation in emissionoutput of the respective colors are similar. This illustrates clearlythat a decrease in total luminous flux and color deviation of athree-wavelength range fluorescent lamp are small, after the lamp hasbeen is use.

                                      TABLE 3                                     __________________________________________________________________________                              Emission                                                                 Mixing                                                                             Output                                                                   Ratio                                                                              After 0 hrs.                                                                             Emission                                 Emitted              (% by                                                                              (Relative Value                                                                          Output                                   Color                weight)                                                                            (%) For Each Color)                                                                      After 500 hrs.                           __________________________________________________________________________    Blue (Ba.sub.0.3 Ca.sub.0.002 Mg.sub.0.6 Eu.sub.0.098)                                             15   100        95                                            O.2.5Al.sub.2 O.sub.3.0.003O0SiO.sub.2                                   Green                                                                              (La.sub.0.5 Ce.sub.0.3 Tb.sub.0.2).sub.2 O.sub.3.                                             50   100        96                                            2.0(Mg.sub.0.999 Ca.sub.0.001)O.8.0[(AlO.sub.3)                               0.9996(SiO.sub.2).sub.0.0004 ]                                           Red  (Y.sub.0.960 Eu.sub.0.040).sub.2 O.sub.3                                                      35   100        98                                       Blue 3(Sr.sub.0.98 Eu.sub.0.02 O).0.92P.sub.2 O.sub.5.                                             19   100        83                                            0.33CaCl.sub.2.0.08B.sub.2 O.sub.3                                       Green                                                                              (La.sub.0.1 Tb.sub.0.2 Ce.sub.0.697                                                           44   100        88                                            Li.sub.0.003).sub.2 O.sub.3.0.9P.sub.2 O.sub.5.0.2SiO.sub.2              Red  (Y.sub.0.950 Eu.sub.0.050).sub.2 O.sub.3                                                      37   100        98                                       __________________________________________________________________________

Table 4 shows the results obtained when the respective phosphors ofTable 3 were removed from the corresponding fluorescent lamps and thereflectances of the lamps were measured. The phosphors of Example 17have higher reflectances than those of Control 4. This is attributableto the following fact.

In a conventional fluorescent lamp, a reaction occurs therein between aconventional phosphor and mercury for excitation during use of the lamp.This degrades the phosphor, resulting in a lower reflectance. Since thereflectance degrades in a similar manner as the emission output does, itis assumed that a degradation in reflectance causes a degradation inemission output.

                  TABLE 4                                                         ______________________________________                                                             Reflectance                                                                             Reflectance                                                         After 0 hrs.                                                                            After 500 hrs.                                 Emitted    Composi-  (Relative (Relative                                      Color      tion      Value)(%) Value)(%)                                      ______________________________________                                        Example 17                                                                    Blue       Same      107       103                                            Green      as        100       95                                             Red        Table 1   103       98                                             Control 4                                                                     Blue                 105       92                                             Green                101       90                                             Red                  103       98                                                        BaSO.sub.4                                                                              100       100                                            ______________________________________                                    

What is claimed is:
 1. A blue emitting phosphor represented by a generalformula (Ba_(w) Ca_(x) Mg_(y) Eu_(z))O.aAl₂ O₃. bSIO₂ where 0.1≦w≦0.5,0.0004≦x≦0.0020, 0.1≦y≦0.8, 0.03≦z≦0.10, w+x+y+z=1, 1.5≦a≦4.5, and0.0005≦b≦0.0030.
 2. A phosphor according to claim 1, wherein 2.0≦a≦3.0,or 0.0006≦x≦0.0015.
 3. A fluorescent lamp comprising a phosphor film onan inner surface of a glass bulb, wherein said phosphor film contains amixture of:a blue emitting first phosphor represented by a generalformula (Ba_(w) Ca_(x) Mg_(y) Eu_(z))O.aAl₂ O₃.bSiO₂ where 0.1≦w≦0.5,0.0004≦x≦0.0020, 0.1≦y≦0.8, 0.03≦z≦0.10, w+x+y+z=1, 1.5≦a≦4.5, and0.0005≦b≦0.0030; a green emitting second phosphor represented by ageneral formula Ln₂ O₃.c(Mg_(1-u) Ca_(u))O.d[(Al₂ O₃)_(1-v) (SiO₂)_(v) ](where Ln is at least one element selected from the group consisting oflanthanum, gadolinium, yttrium, cerium, and terbium, and 1.5≦c≦5.0,2.5≦d≦14.0, 0.001≦u≦0.005, and 0.0002≦v≦0.0010); and a red emittingthird phosphor represented by a general formula (Y_(1-t) Eu_(t))₂ O₃(where 0.020≦t≦0.065), the first, second, and third phosphors beingcontained in ratios of 0.2 to 35% by weight, 35 to 60% by weight, and 30to 60% by weight, respectively, with respect to 100% by weight of themixture.